(See also Overview of Transplantation Overview of Transplantation Transplantation is the removal of living, functioning cells, tissues, or organs from the body and then their transfer back into the same body or into a different body. The most common type of... read more .)
Stem cells are unspecialized cells from which other more specialized cells can be derived. Stem cells may be obtained from
Blood removed from a vein
Bone marrow (bone marrow transplantation)
Blood in the umbilical cord of a baby after it is born (donated by the mother)
Blood is preferred to bone marrow as a source because the procedure is less invasive and the number (count) of blood cells returns to normal more quickly. Stem cells from umbilical cords are usually used only in children because umbilical cord blood does not contain enough stem cells to use in adults.
Although stem cells in theory can become any other type of cell, in practice, stem cell transplantation is used mainly as part of the treatment for blood disorders such as leukemia Overview of Leukemia Leukemias are cancers of white blood cells or of cells that develop into white blood cells. White blood cells develop from stem cells in the bone marrow. Sometimes the development goes awry... read more , certain types of lymphoma (including Hodgkin lymphoma Hodgkin Lymphoma Hodgkin lymphoma is a cancer of a type of white blood cell called lymphocytes and is distinguished from other lymphomas by the presence of a particular kind of cancer cell called a Reed-Sternberg... read more ), aplastic anemia Aplastic Anemia Aplastic anemia is a disorder in which the cells of the bone marrow that develop into mature blood cells are damaged, leading to low numbers of red blood cells, white blood cells, and/or platelets... read more , thalassemia Thalassemias Thalassemias are a group of inherited disorders resulting from an imbalance in the production of one of the four chains of amino acids that make up hemoglobin (the oxygen-carrying protein found... read more , sickle cell disease Sickle Cell Disease Sickle cell disease is an inherited genetic abnormality of hemoglobin (the oxygen-carrying protein found in red blood cells) characterized by sickle (crescent)-shaped red blood cells and chronic... read more . Sometimes stem cell transplantation is used for congenital metabolic or immunodeficiency disorders (such as chronic granulomatous disease Chronic Granulomatous Disease (CGD) Chronic granulomatous disease is a hereditary immunodeficiency disorder in which phagocytes (a type of white blood cell) malfunction. People with chronic granulomatous disease have persistent... read more ).
Stem cell transplants may also be given to people who have been treated with high doses of chemotherapy or radiation therapy for certain cancers. Such treatments destroy bone marrow, which produces stem cells. Occasionally, stem cell transplants can be used to replace bone marrow cells that are destroyed during treatment of cancers in organs, such as breast cancer or neuroblastoma (a common childhood cancer that develops from nerve tissue). Doctors are studying how to use stem cell transplantation to treat some autoimmune disorders, such as multiple sclerosis.
About 30 to 40% of people who had lymphoma and 20 to 50% of those who had leukemia are cancer-free after treatments, including stem cell transplantation. The procedure prolongs life in people with multiple myeloma. It is less effective for breast cancer.
Procedure for Stem Cell Transplantation
Stem cells may be
The person’s own cells (autologous transplantation)
Those of a donor (allogeneic transplantation)
If people with cancer are being given their own stem cells, the cells are collected before chemotherapy or radiation therapy, which can damage stem cells. The cells are injected back into the body after the treatment.
If the stem cells come from a donor, the recipient is given drugs to suppress the immune system (immunosuppressants Suppression of the Immune System Transplantation is the removal of living, functioning cells, tissues, or organs from the body and then their transfer back into the same body or into a different body. The most common type of... read more ) before stem cells are transplanted.
If the stem cells are intended to replace the blood-forming cells in the recipient's bone marrow, the recipient is given a combination of drugs and radiation treatments to eliminate bone marrow cells that would keep the transplanted cells from surviving.
Stem cells from blood
Stem cells from adults can be obtained from blood during an outpatient procedure. First, a few days before stem cells are obtained, the donor is given drugs that cause the bone marrow to release more stem cells into the bloodstream (called colony-stimulating factors). Then blood is removed through a catheter inserted in one arm and is circulated through a machine that removes stem cells. The rest of the blood is returned to the person through a catheter inserted in the other arm. Usually, about six 2- to 4-hour sessions over a period of several days are needed, until enough stem cells are obtained. Stem cells can be preserved for later use by freezing them. Stem cells can also be obtained from the umbilical cord of a baby after delivery and frozen for future use.
Stem cells from bone marrow
For bone marrow transplantation, the donor is given a general or local anesthetic. Doctors then remove marrow from the donor’s hip bone with a syringe. Removal of bone marrow takes about 1 hour.
Stem cells are injected into the recipient’s vein over a period of 1 to 2 hours. The injected stem cells migrate to and begin to multiply in the recipient’s bones and produce blood cells.
After the stem cell transplantation
After transplantation, drugs are given to prevent complications (see below).
Recipients of a stem cell transplant usually remain in the hospital for 1 to 2 months.
After discharge from the hospital, follow-up visits are scheduled at regular intervals. Most people need at least 1 year to recover.
Complications of Stem Cell Transplantation
Stem cell transplantation is risky because the recipient’s white blood cells have been destroyed or reduced in number by chemotherapy or radiation therapy. As a result, the risk of infection is very high for about 2 to 3 weeks—until the donated stem cells can produce enough white blood cells to protect against infections.
The risk of infection can be reduced by keeping the recipient in isolation for a period of time (until the transplanted cells begin to produce white blood cells). During this time, everyone entering the room must wear masks and gowns and wash their hands thoroughly.
The recipient is given
Colony-stimulating factors, which stimulate the production of blood cells (including white blood cells, which help fight infection)
Antimicrobial drugs to help reduce the risk of infection
The new bone marrow obtained from another person may produce cells that attack the recipient’s cells, causing graft-versus-host disease Graft-versus-host disease Transplantation is the removal of living, functioning cells, tissues, or organs from the body and then their transfer back into the same body or into a different body. The most common type of... read more . This disease causes death in about 20 to 40% of people who develop it.
So if the bone marrow came from another person, recipients are given immunosuppressants Suppression of the Immune System Transplantation is the removal of living, functioning cells, tissues, or organs from the body and then their transfer back into the same body or into a different body. The most common type of... read more to prevent graft-versus-host disease and rejection.
Recurrence of the original disorder
Whether the original disorder returns depends on
What the original disorder was
How severe it was
What type of transplant was used
The original disorder returns in
40 to 75% of people who are given their own stem cells
10 to 40% of people who are given stem cells from other people